Men, we have an amazing dual purpose organ known as the Penis.  We use it for removal of liquid body waste as well as a vehicle for pleasure and procreation.  But do we know what’s inside? Inside, the penis is made up of 3 columns of tissue as well as veins and arteries.   The corpora cavernosa are 2 columns of spongy erectile tissue which lie next to each other on the dorsal (tope when erect) side of the penis. The corpus spongiosum lies in between them on the ventral (bottom when erect) side of the penis.  When blood enters the penis during an erection, the corpora cavernosa hold 90% of the blood.  The corpus spongiosum remains pliable and keeps the urethra from pinching closed during erection to maintain a viable channel for ejaculation.  There are 3 brain centers that regulate urination.  During erection these centers block the relaxation of the urethral sphincter muscle in order to keep a physiological separation between urination and ejaculation. So now that you have the short and sweet version of the inside story, you have a better understanding of how the Penis works.  For more information about the penis, particularly with regard to size or dysfunction, check this website https://www.loriamedical.com.